Electric vacuum pump

ABSTRACT

An electric vacuum pump includes: a motor part and a pump part placed in a case, and a cover member closing the case from a pump part side. The cover member includes: a suction port for sucking a fluid from pump outside into the pump part; a silencer part including a space part communicating with a discharge outlet of the pump part; and a discharge port for discharging a fluid ejected from the pump part to pump outside. The suction port has an end portion placed in sealingly contact with the pump part to hermetically communicate with a suction inlet of the pump part. The discharge port is formed with a throat part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2012-236367 filed on Oct. 26, 2012, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vacuum pump for generating negative pressure to be used in a brake booster of a vehicle such as a motorcar.

2. Related Art

A brake device for vehicle is provided with a brake booster for amplifying a braking force by utilizing negative pressure in an intake pipe (“intake-pipe negative pressure”) of an engine. In recent years, pumping loss is reduced in response to demands for low-fuel consumption and thus the negative pressure in the intake pipe tends to decrease. Furthermore, for a hybrid vehicle, an electric vehicle, or a vehicle with an idling stop function, there is a case where the intake-pipe negative pressure of an engine could not be obtained.

Accordingly, the negative pressure to be supplied to a brake booster is generated by use of an electric vacuum pump. In a vehicle mounting a diesel engine that generates no intake-pipe negative pressure, negative pressure is also generated by use of an electric vacuum pump.

One example of such as a vacuum pump is disclosed in for example Patent Document 1. This pump includes a case having an internal space, a cylindrical moving member placed to be eccentrically movable within the internal space, a cover placed in the case to close the internal space at one end thereof, and a deformable member fixed to the case and the moving member so as to be deformed in association with eccentric movement of the moving member. The cover has two ports for fluid. The deformable member generates a pump space around the moving member so that the volume of the pump space varies with the eccentric movement of the moving member.

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: JP 9(1997)-296784A

SUMMARY OF INVENTION Problems to be Solved by the Invention

However, the pump disclosed in Patent Document 1 does not include a silencing function and causes large operation sound. In particular, in a case where this pump is used in a brake system of a vehicle such as a motorcar, it is necessary to extremely reduce the operation sound. It is further desired to improve mountability and installability on vehicles.

The present invention has been made to solve the above problems and has a purpose to provide an electric vacuum pump with sound-reducing (anti-noise) measure by a simple structure to minimize operation sound or noise.

Means of Solving the Problems

To achieve the above purpose, one aspect of the invention provides an electric vacuum pump including: a resin case having internal space; a motor part placed in the internal space of the case, a pump part placed in the internal space of the case and arranged to drive in sync with the motor part, and a cover member closing the internal space of the case from a pump part side, wherein the cover member includes: a suction port for sucking a fluid from outside of the pump into the pump part; a silencer part including a space part communicating with a discharge outlet of the pump part; and a discharge port for discharging a fluid ejected from the pump part to outside of the pump, the suction port has an end placed in sealingly contact with the pump part to hermetically communicate with a suction inlet of the pump part, and the discharge port is formed with a throat part.

Effects of the Invention

The electric vacuum pump of the invention, as explained above can be provided with sound-reducing measure by a simple structure and minimize operation sound or noise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration view of a brake system including an electric vacuum pump in an embodiment;

FIG. 2 is a block diagram showing a control system of the brake system including the electric vacuum pump in the embodiment;

FIG. 3 is a front view of the electric vacuum pump in the embodiment;

FIG. 4 is a top view of the electric vacuum pump in the embodiment;

FIG. 5 is a cross sectional view taken along a line A-A in FIG. 4; and

FIG. 6 is a view showing a modified example of an electric vacuum pump.

DESCRIPTION OF EMBODIMENTS

A detailed description of a preferred embodiment of an electric vacuum pump embodying the present invention will now be given referring to the accompanying drawings. The present embodiment shows a case where the electric vacuum pump according to the invention is applied to a brake system.

Thus, the brake system is firstly explained referring to FIGS. 1 and 2. FIG. 1 is a schematic configuration view of the brake system including the vacuum pump in the present embodiment. FIG. 2 is a block diagram showing a control system of the brake system including the electric vacuum pump in the present embodiment.

A brake system 1 in the present embodiment includes, as shown in FIGS. 1 and 2, a brake pedal 10, a brake booster 12, a master cylinder 14, a negative pressure sensor 16, an electric vacuum pump 18 (labeled “Electric VP” in the figure), a first check valve 20, a second check valve 22, an ECU 24, an intake pipe pressure detection unit 26, and an engine stop determination unit 28, and others.

The brake booster 12 is provided between the brake pedal 10 and the master cylinder 14 as shown in FIG. 1. This brake booster 12 generates an assist force at a predetermined boosting ratio to a tread force on the brake pedal 10.

The brake booster 12 is internally partitioned by a diaphragm (not illustrated) into a negative pressure chamber (not shown) close to the master cylinder 14 and a transformer chamber (not shown) allowing introduction of atmospheric air. The negative pressure chamber of the brake booster 12 is connected to an intake pipe 32 of an engine through a first passage L1. Specifically, the first passage L1 is connected to the negative pressure chamber of the brake booster 12 and the intake pipe 32. Accordingly, the negative pressure chamber of the brake booster 12 is supplied with negative pressure generated in the intake pipe 32 through the first passage L1 according to an opening degree of a throttle valve 34 during driving of the engine.

The master cylinder 14 increases oil pressure of a brake main body (not shown) by operation of the brake booster 12, thereby generating a braking force in the brake main body. The negative pressure sensor 16 detects the negative pressure in the negative pressure chamber of the brake booster 12.

The electric vacuum pump 18 is connected to the second passage L2 as shown in FIG. 1. Specifically, a suction port 141 of the electric vacuum pump 18 is connected to the negative pressure chamber of the brake booster 12 through the second passage L2 and the first passage L1. It is to be noted that a discharge port 142 of the electric vacuum pump 18 is connected to the intake pipe 32 upstream of the throttle valve 34 and is open to the atmosphere. Herein, the second passage L2 is a pathway for branching from the first passage L1 at a position on the first passage L1 between the first check valve 20 and the second check valve 22.

Furthermore, the electric vacuum pump 18 is connected to the ECU 24 through a motor part 110 (electric motor 112) and a relay 36 as shown in FIG. 2. Driving of the electric vacuum pump 18 is controlled by ON/OFF operation of the relay 36 by the ECU 24.

The first check valve 20 is provided in the first passage L1 at a position between a branch point to the second passage L2 and the brake booster 12. The second check valve 22 is provided in the first passage L1 at a position closer to the intake pipe 32 than the first check valve 20 and between the branch point to the second passage L2 and the intake pipe 32. These first check valve 20 and second check valve 22 are each configured to open only when negative pressure on the side of the intake pipe 32 is higher than the negative pressure on the side of the negative pressure chamber of the brake booster 12 and to permit a fluid to flow only from the negative pressure chamber of the brake booster 12 to the intake pipe 32. In this manner, the brake system 1 can encapsulate negative pressure in the negative pressure chamber of the brake booster 12 by the first check valve 20 and the second check valve 22.

The ECU 24 consists of for example a microcomputer and includes a ROM that stores control programs, a rewritable RAM that stores calculation results and others, a timer, a counter, an input interface, and an output interface. To this ECU 24, as shown in FIG. 2, there are connected the negative pressure sensor 16, the electric vacuum pump 18, the intake pipe pressure detection unit 26, the engine stop determination unit 28, the relay 36, and others.

Herein, the electric vacuum pump 18 will be explained referring to FIGS. 3 to 5. FIG. 3 is a front view of the electric vacuum pump in the present embodiment. FIG. 4 is a top view of the electric vacuum pump in the present embodiment. FIG. 5 is a cross sectional view taken along a line A-A in FIG. 4.

The electric vacuum pump 18 has a cylindrical shape as shown in FIGS. 3 and 4 and is provided with the suction port 141 and the discharge port 142 at an upper end and a connector 118 at a lower end. This electric vacuum pump 18 includes the motor part 110, a pump part 120, a resin case 130, a resin upper cover 140, and a resin lower cover 160. Further, as shown in FIG. 5, the motor part 110 and the pump part 120 are housed in the case 130. The case 130 containing the motor part 110 and the pump part 120 is closed by the upper cover 140 and the lower cover 160.

The motor part 110 includes an electric motor 112, a metal motor case 114, a rotary shaft 116, and the connector 118. The electric motor 112 is housed in the motor case 114 and includes a stator 112 a and a rotor 112 b. The stator 112 a is fixed to the motor case 114 so that the rotor 112 b is rotatably placed inside the stator 112 a with a clearance therefrom.

The rotary shaft 116 is attached to this rotor 112 b. The connector 118 including terminals 118 a for supplying electric power to the electric motor 112 (the stator 112 a) is provided on the lower cover 160. Accordingly, in the motor part 110, the electric motor 112 is driven by an external power supply connected through the connector 118 to drive the rotary shaft 116 to rotate. The rotary shaft 116 is rotatably supported by a bearing fixed to the motor case 114.

The pump part 120 is constituted of a vane-type vacuum pump and is placed above the motor part 110 in the case 130. Herein, the vane-type vacuum pump is configured such that a rotor having a circular columnar shape placed in an eccentric state in a pump chamber is formed with grooves, in which a plurality of vanes are inserted to be movable in a rotor radial direction. When the rotor rotates, the vanes are caused to protrude from the grooves by centrifugal force and slide in contact with the inner peripheral surface of the pump chamber, thereby maintaining hermetical sealing between adjacent small chambers of the pump chamber. In association therewith, the volume of each closed space or small chamber partitioned by the vanes is increased or decreased, thereby causing suction, compression, and discharge of air, so that negative pressure is generated in the pump chamber.

To be concrete, the pump part 120 is provided with a housing 121 having an inner peripheral surface of a nearly cylindrical shape. The inner peripheral surface of a nearly cylindrical shape represents that the cross section of the housing is defined in a circular shape surrounded by a curved line without being limited to a perfect circular or elliptic shape. Both ends of the housing 121 are closed by circular cover members 122 a and 122 b, so that a pump chamber 123 is formed by the inner peripheral surface of the housing 121 and the cover members 122 a and 122 b. The housing 121 is fixed to the case 130.

In the pump chamber 123, a circular columnar rotor 124 is housed to be rotatable about the axis eccentric to the center axis of the pump chamber 123. This rotor 124 is coupled to the rotary shaft 116 of the electric motor 112. Accordingly, the rotor 124 is rotated in sync with rotary driving of the electric motor 112 via the rotary shaft 116.

The rotor 124 has a plurality of vane grooves formed radially extending from the axis in a radial direction. In the vane groove, vanes 125 each formed in a flat plate shape are slidably engaged to be movable in and out in the radial direction of the circular columnar rotor 124. Those vanes 125 are arranged radially and spaced circumferentially at equal intervals. A radially outer end of each vane 125 slides in contact with the inner peripheral surface of the housing 121 by centrifugal force imparted to the vanes 125 during rotation of the rotor 124. Upper and lower end faces of the vanes 125 are in contact with the cover members 122 a and 122 b respectively. Thus, the vanes 125 partition the pump chamber 123 into a plurality of small chambers or spaces.

The pump chamber 123 communicates with the outside through a suction inlet 126 and a discharge outlet 127. The suction inlet 126 is provided in the cover member 122 a and communicated with the pump chamber 123. The suction inlet 126 is hermetically closed by an end of the suction port 141 sealingly connected to the cover member 122 a to suck air from pump outside (the outside of the electric vacuum pump 18) into the pump chamber 123. Similarly, the discharge outlet 127 is also provided in the cover member 122 a and communicated with the pump chamber 123. Exhaust air ejected from the discharge outlet 127 is discharged to the pump outside through the discharge port 142.

The upper cover 140 is a resin member closing an upper open end of the case 130 that houses the motor part 110 and the pump part 120. The upper cover 140 is one example of a “cover member” of the invention. Specifically, the upper cover 140 closes the case 130 from the pump part side (from above in FIG. 5).

This upper cover 140 is provided with the suction port 141 to suck air in the pump part 120 from the pump outside, an inlet pipe 141 a constituting part of the suction port 141, a silencer part 143 including a space or cavity communicating with the discharge outlet 127 of the pump part 120, the discharge port 142 to discharge exhaust air discharged or ejected from the pump part 120 to the pump outside, and a throat part 142 a provided in the discharge port 142. Those suction port 141, inlet pipe 141 a, discharge port 142, and throat part 142 a are made together with the upper cover 140 by integral molding. Accordingly, joining of the upper cover 140 with the case 130 housing the motor part 110 can be made by welding without using screws or the like. In the present embodiment, outer circumferential end faces of the upper cover 140 and the case 130 are joined to each other by ultrasonic welding. This can result in a reduction in number of components of the electric vacuum pump 18 and an increase in productivity thereof, leading to cost reduction.

The silencer part 143 is formed by the internal space of the upper cover 140. The throat part 142 a is formed in the discharge port 142. Thus, exhaust air discharged or ejected from the discharge outlet 127 of the pump part 120 passes through the silencer part 143, flows through the throat part 142 a, and then is discharged to the pump outside. Thus, the exhaust air can be repeatedly exposed to loads, so that pump operation sound or noise can be reduced to a minimum. In this manner, the electric vacuum pump 18 can be effectively provided with the sound-reducing measure by a very simple structure.

The shape of the throat part 142 a is not particularly limited to the above. It may be a shape that an entire discharge port is narrowed to form a throat as shown in FIG. 5 or a shape that part of the discharge port is narrowed or constricted.

Furthermore, the suction port 141 and the discharge port 142 provided in the upper cover 140 are located within a project plane of the electric vacuum pump 18 with respect to the pump axial direction (longitudinal direction) (see FIG. 4). In other words, the suction port 141 and the discharge port 142 are arranged so as not to project outward from the outer diameter of the electric vacuum pump 18. Accordingly, when the electric vacuum pump 18 is to be mounted on a vehicle, the suction port 141 and the discharge port 142 will not interfere with other components or parts, resulting in improved mountability. An orientation of the electric vacuum pump 18 to be mounted on a vehicle is not particularly limited.

Moreover, the suction port 141 and the discharge port 142 are arranged on an upper end of the upper cover 140 (one end of the vacuum pump in the axial direction) so that their open ends face in the same direction (on the near side of a drawing sheet of FIG. 3). This can facilitate a piping work in mounting the electric vacuum pump 18 on a vehicle and thus improve installability.

The lower cover 160 is a resin member closing a lower open end of the case 130 that houses the motor part 110 and the pump part 120. The lower cover 160 closes the case 130 from the motor part side (from below in FIG. 5).

This lower cover 160 is provided, by integral molding, with the connector 118 including the terminals 118 a extending from the motor part 110.

Accordingly, joining of the lower cover 160 with the case 130 housing the motor part 110 can be made by welding without using screws. In the present embodiment, outer circumferential end faces of the lower cover 160 and the case 130 are joined to each other by ultrasonic welding. This can result in a reduction in number of components of the electric vacuum pump 18 and an increase in productivity thereof, leading to cost reduction.

The connector 118 provided in the lower cover 160 is arranged to face in the same direction as the open ends of the suction port 141 and the discharge port 142. This can facilitate an electric wiring work in mounting the electric vacuum pump 18 on a vehicle and thus improve installability.

In the electric vacuum pump 18 configured as above, when the electric motor 112 is driven to rotate upon receipt of power from an external source, the rotor 124 is rotated in synchronization therewith. Then, the vanes 125 slide along the vane grooves by centrifugal force, causing the end faces of the vanes 125 to contact with the inner peripheral surface of the housing 121. While keeping such a contact state, the vanes 125 are rotated along the inner peripheral surface of the housing 121. This rotation of the rotor 124 causes the volume of each small chamber of the pump chamber 123 to expand or contract, thereby sucking air into the pump chamber 123 through the suction inlet 126 and ejecting air from the pump chamber 123 through the discharge outlet 127. This operation generates negative pressure in the pump chamber 123.

Specifically, in the brake system 1, when the relay 36 is turned on based on a drive start signal from the ECU 24, the electric vacuum pump 18 starts operating, thereby supplying negative pressure to the negative pressure chamber of the brake booster 12 through the suction port 141, the second passage L2 and the first passage L1. Furthermore, when the relay 36 is turned off based on a drive stop signal from the ECU 24, the electric vacuum pump 18 stops operating, thereby stopping supplying negative pressure to the negative pressure chamber of the brake booster 12 through the suction port 141, the second passage L2 and the first passage L1.

In the brake system 1, in a case where the engine is running and negative pressure is generated in the intake pipe, the negative pressure in the intake pipe 32 is supplied to the negative pressure chamber of the brake booster 12 through the first passage L1 to regulate the negative pressure in the negative pressure chamber of the brake booster 12. In a case where the engine is stopped and in a case where the ECU 24 determines that the negative pressure is insufficient, the ECU 24 turns on the relay 36, thereby driving the electric vacuum pump 18 to supply the negative pressure to the negative pressure chamber of the brake booster 12 through the second passage L2 and the first passage L1. Thus, the negative pressure in the negative pressure chamber of the brake booster 12 can be regulated.

According to the electric vacuum pump 18 in the present embodiment as explained in detail above, the sound-reducing measure is achieved by a very simple configuration that the suction port 141 and the discharge port 142 are provided in the upper cover 140, the upper cover 140 is internally formed with the space or cavity providing the silencer part 143, and the throat part 142 a is formed in the discharge port 142. This configuration can minimize operation sound or noise of the pump.

The aforementioned embodiment is a mere example and does not limit the scope of the invention. The present invention may be embodied in other specific forms without departing from the essential characteristics thereof.

For instance, the above embodiment uses the case 130 having a stepped outer shape different in diameter between a part housing the pump part and a part housing the motor part. An alternative is to use a case 130 a having a straight shape with no step, substantially equal in diameter between a pump part and a motor part, as shown in FIG. 6. This can achieve more improved mountability in mounting an electric vacuum pump on a vehicle. 

1. An electric vacuum pump including: a resin case having internal space; a motor part placed in the internal space of the case, a pump part placed in the internal space of the case and arranged to drive in sync with the motor part, and a cover member closing the internal space of the case from a pump part side, wherein the cover member includes: a suction port for sucking a fluid from outside of the pump into the pump part; a silencer part including a space part communicating with a discharge outlet of the pump part; and a discharge port for discharging a fluid ejected from the pump part to outside of the pump, the suction port has an end placed in sealingly contact with the pump part to hermetically communicate with a suction inlet of the pump part, and the discharge port is formed with a throat part.
 2. The electric vacuum pump according to claim 1, wherein the suction port and the discharge port are arranged in a project plane of the electric vacuum pump in an axial direction of the electric vacuum pump.
 3. The electric vacuum pump according to claim 1, wherein the cover member is made of resin by integral molding.
 4. The electric vacuum pump according to claim 1, wherein the suction port, the discharge port, and the throat part are made together with the cover member by integral molding.
 5. The electric vacuum pump according to claim 1, wherein the suction port and the discharge port are placed on one end in an axial direction of the electric vacuum pump so that open ends of the suction port and the discharge port face in the same direction. 